Actually, that picture looks very much like it might just be gathered at the top of the bell. You know, just knit in a straight tube, from the bottom up, and then decreased dramatically in the last couple rows, to bring it in to arm width. It's knit in a lacey pattern that allows it to be gathered in this way. If it were a more solid-pattern bell, it wouldn't gather in well. The lacey holes make it work.
You could test how well the fabric will gather, just by bunching it together on the needles.